Therapeutic method for enhancing saliva

ABSTRACT

The present invention relates to a therapeutic composition comprising an aqueous solution of at least one polymer and at least one electrolyte, wherein the aqueous solution is preferably buffered and optionally contains at least one mucin. The polymer can be chosen for instance from the group which consists of scleroglucan, guar gum, xanthane gum, sodium carboxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid and polyvinyl alcohol. The therapeutic composition according to the invention can serve as saliva substitution agent, artificial tear water, in a mouth rinse or in a toothpaste.

This application is a 371 PCT/NL95/00046 filed Feb. 2, 1995.

The present invention relates to a therapeutic composition for replacingand/or supplementing body fluids such as saliva and tears.

Saliva, tears and the like are of importance for maintaining a healthyenvironment in the mouth and eyes. It is not however self-evident thatan individual can produce sufficient tear water or saliva. People whohave had radiation treatment of the oral cavity, cervix or throat arefor instance often no longer capable of producing sufficient saliva,because their salivary glands have been entirely or partially destroyedby the radiation treatment.

Another example is formed by those suffering from Sjogren syndrome, whomay display symptoms like dry mouth and dry eyes in addition torheumatic disorders. Sjogren syndrome is a progressive process which hasa gradual adverse effect on the saliva production. 60% of the patientsconsists of women after the menopause. Sjogren syndrome is suspected ofbeing an autoimmune disease.

Dry mouth also occurs regularly in users of medicine, particularly usersof sedatives, β-blockers, antihypertension medication, tranquilizers andothers medicines which have the side-effect of dulling the nervoussystem.

A shortage of saliva or tear water can, in addition to the accompanyingdiscomfort and irritation, moreover result in inflammations of the mouthand eyes.

In order to relieve the complaints of dry mouth and eyes salivasubstitutes based on carboxymethyl cellulose (CMC) or animal mucins havebeen proposed (Levine et al., J. Dent. Res. 66:693-698 (1987)). Inaddition a saliva substitute based on linseed-extract is described inEP-0.511.181. In practice however these known substitutes are not foundto be satisfactory. The effective duration of these products is onlylimited and compared to human saliva they do not possess the desiredproperties, such as elasticity, viscosity etc.

The object of the present invention is to provide a saliva substitutewhich approximates the properties of human saliva better than the knownproducts, eliminates the dry sensation in mouth and eyes and needs to beapplied less often.

To this end the invention provides a therapeutic composition, comprisinga buffered, aqueous solution of at least one polymer and at least oneelectrolyte.

The polymer is preferably chosen from the group which consists ofscleroglucan (in a concentration of about 0.001% to 2% (w/v)), guar gum(about 0.001% to 5% (w/v)), xanthane gum (about 0.001% to 2% (w/v)),sodium carboxymethyl cellulose (for instance of the type Blanose® 7HF,in a concentration of 0.01 to 5% (w/v)), hydroxyethyl cellulose (forinstance of the type Natrosol 250 HX Pharm, in a concentration of 0.01to 5% (w/v)), polyacrylic acid (for instance of the types Carbopol 934P®and Carbopol 974P®, in a concentration of 0.01 to 5% (w/v)) andpolyvinyl alcohol (for instance with a degree of hydrolysis between 71.6and 100 mol %, an ester value between 0 and 285 g KOH/g, a molecularweight between 14,000 and 205,000 and a degree of polymerization between360 and 4500). Another suitable product can however be chosen as desiredfrom the large supply of available polymers, and particularlypolysaccharides.

At least one mucin can optionally be added to the composition. Theelectrolyte can for instance be chosen from the group consisting ofsodium, potassium, fluoride, chloride, phosphate, CNS, rhodanide. Thecomposition can further also contain calcium and/or at least onephosphate compound, as well as flavourings and/or aromatic substancesand/or colourings and preservative.

The invention further relates to saliva substitutes or additives,artificial tear water or tear additives, mouth rinses and toothpastes,comprising the therapeutic composition according to the invention.

The advantages of the present invention will become apparent from theexample hereinbelow, which is however only intended as illustration andfurther implies no limitation whatever to the scope of the invention.

EXAMPLE 1

1. Materials

Xanthane gum (95465) originated from Fluka. Alginic acid with a highviscosity (9005-38-3/A-7128) was supplied by Sigma. Carboxymethylcellulose (Blanose® 7HF) and hydroxyethyl cellulose (Natrosol 250HX-Pharm) were donations from Aqualon, Rijswijk, the Netherlands.Scleroglucan (Actigum CS11) and Guar gum (Viscogum HV 3 000A) came fromSatia, Paris, France. A second type of guar gum (#21255) came fromPolysciences Inc., Warrington Pa., USA. All other chemicals came fromMerck and were of analytical quality.

2. Sample preparation

All polysaccharides were used directly and dissolved in HPLC-water (J.T.Baker Company, Philipsburg, USA) in the desired concentration.Polysaccharide solutions were obtained by adding the dry polymer base towater while stirring vigorously. After dispersion the solutions wereplaced on a shaking table for 18 hours to obtain a homogeneous solution.

For the pH-dependency experiments the pH was varied between 3 and 9 byadding NaOH or Hcl. To keep the ionic strength uniform, NaCl was addedto the highest added NAOH or Hcl concentration.

The effect of the ionic strength on the rheological properties ofpolysaccharides was studied by varying the ionic strength between 0 and500 Mm NaCl.

All polysaccharides were tested for their rheological behaviour aftercalcium or fluoride treatment and for. their biocompatibility withcomplete human saliva. The influence of calcium ions and fluoride ionswas studied by adding respectively CaCl₂ (0-0.5M), NaF (0.6 Mm) to thechosen polysaccharide solutions (Worthington et al., in press (1993)).

After addition of NaOH, Hcl or CaCl₂ the solution was incubated at roomtemperature for three hours.

Determination of the rheological synergistic effects was carried out bymixing equal volumes of polysaccharide solution and non-stimulatedcomplete saliva. Mixtures of water and polymer, and water and salivaserved as control. To prevent bacterial and fungal growth in the testsamples, the polysaccharide solutions were freshly prepared for eachexperiment.

Complete human saliva (CHS) was collected by spitting out without anykind of stimulation. It was clarified by centrifugation in a MSEMicro-centaur centrifuge (MSE Scientific Instruments, Sussex, UnitedKingdom) at 11,600 g at room temperature for 5 minutes and was usedimmediately for Theological measurements. Clarified complete humansaliva is denoted as CCHS.

3. Rheological measurements

In this study an oscillating capillary rheometer was used to determinethe viscous part η' and the elastic part η" of the complex viscosity η*as already described (Van der Reijden et al., Biorheol. 30:141-152(1993)).

The rheometer was a Vilastic 3 visco-elasticity analyser from VilasticScientific Inc., Austin, USA. Comparisons of viscosity and elasticity asin table 2 are made at a shear rate of 1.5 sec⁻¹. All measurements wereperformed at a frequency of 0.5 Hz and at a shear rate between 1 and1000 s⁻¹ and at room temperature (23.0° C.±1.5° C.).

4. Results

The saliva of 7 people was used as reference. A sample was taken fromeach person three times. The average values of the visco-elasticitymeasurements of the clarified complete human saliva are shown in FIG. 1.

Inter-individual differences were observed in viscosity as well aselasticity, which are shown by error bars representing twice thestandard deviation. The data was obtained from an earlier study (Van derReijden et al., 1993). It is noteworthy that the viscosity of completehuman saliva is only a little pseudoplastic and about 2.07±0.48 mPa·s.The elasticity of complete human saliva is reasonably high compared toits viscosity: 0.77±0.31 Mpa·s. The shear rate dependency of theviscosity of the various polysaccharides tested is shown in FIG. 2, andthat of the elasticity in FIG. 3. The shear rate dependency is apparentfor all polysaccharides at a concentration of 0.1%. At a concentrationwhich resulted in a viscosity level corresponding with natural saliva,`pseudoplasticity` was observed for the viscosity and elasticity ofxanthane gum and scleroglucan, but hardly so for the otherpolysaccharides (FIGS. 2 and 3).

A number of polysaccharides exhibited fluctuations in visco-elasticityby varying the pH between 5 and 9, as shown in table 1. Xanthane gum andCMC displayed a slight increase in visco-elasticity in the pH rangebelow pH 5 respectively 6. Alginic acid was very sensitive to pH changes(FIGS. 4 and 5). The visco-elasticity of polysaccharides can besensitive to changes in ionic strength, mainly due to their hydrationshell, which is dependent on the molecular weight, the form, the extentand type of substitution. Xanthane gum, alginic acid and CMC wererelatively stable at more than 10 mM NaCl, while scleroglucan, guar gumand HEC were even rheologically stable between 0 and 0.2M NaCl (FIGS. 6and 7) and further in the direction of 0.5M NaCl (not shown). Althoughall polysaccharides displayed an elastic response at a concentration of0.1%, particularly the `natural` polysaccharides scleroglucan andxanthane gum were elastic at relatively low (saliva) viscosity at aphysiological pH (5-9) and at a physiological ionic strength (15-80 mM)(table 2 and FIG. 3).

Because calcium and fluoride ions are preferably added to a salivasubstitute to remineralize the human enamel, the influence of these ionson the rheology was likewise investigated. Apart from alginic acid noneof the polysaccharides displayed a specific ion-related behaviour. Thepolysaccharides alginic acid, xanthane gum and CMC, which were ionicstrength sensitive for NaCl, were also sensitive to Ca²⁺ and F⁻.Precipitate formation of polysaccharide molecules on calcium ions wasonly observed in alginic acid, which even became completely insolublethrough addition of trace amounts of CaCl₂ (Smidsrφc, et al., Acta ChemScand. 26:2563-2566 (1972)). It was notable that no complex formingoccurred of alginic acid with CCHS, although human saliva is asupersaturated calcium solution.

                                      TABLE 1    __________________________________________________________________________    A number of parameters which could have influ-    enced the tested polysaccharides. - respectively + repre-    sent a decrease respectively increase in visco-elastici-    ty,  represents no change in visco-elasticity.                  ionic strength                          Ca.sup.2+                                  F    Influence on    Polysaccharide               pH (0-0.5 M NaCl)                          (0-0.5 M CaCl.sub.2)                                  (0.06 mM)                                       saliva    __________________________________________________________________________    Alginic acid               ≦5                  --      flocculation                                  --    Carboxymethyl cellulose               ≦6                  --                                        --       Hydroxyethyl cellulose                                                                                                                                        Guar gum (Satia)                                                                                                                                        Guar gum (Polysciences                                                                                                                                        Inc.)    Scleroglucan                                                                                                                                    +*/    Xanthanegum               ≦5                  --                                                                                   __________________________________________________________________________     *Only observed for a scleroglucan concentration of at least 0.1%.

                  TABLE 2    ______________________________________    Survey of the rheological properties of tested    polysaccharides at a concentration of 0.1% and at a    polymer-specific saliva simulating concentration Y = 1.5    s.sup.-1, T = 23.0° C. ± 1.5° C., ionic strength = 10 mM    NaCl.                    Conc.              Conc.    Polysaccharides %      η' η"                                       (%)  η'                                                η"    ______________________________________    Alginic acid    0.1    3.4    0.13 0.05 1.8 0.05    Carboxymethyl cellulose                    0.1    5.1    0.38 0.03 1.7 0.10    Hydroxyethyl cellulose                    0.1    3.0    0.09 0.06 1.8 0.05    Guar gum (Satia)                    0.1    1.5    0.04 0.1  1.5 0.04    Guar gum (Polysciences Inc.)                    0.1    2.1    0.07 0.09 2.0 0.07    Scleroglucan    0.1    20.6   38.6 0.01 1.3 0.31    Xanthane gum    0.1    22.8   23.9 0.01 1.6 028    Clarified complete human saliva         2.1 0.77    ______________________________________

5. Discussion

Earlier research has demonstrated that the rheological properties ofsaliva from the different glands varies markedly. In particular thesublingual saliva was found to be very elastic (Van der Reijden et al.,1993). It is therefore not possible to create a saliva substitute whichreflects all Theological properties of the salivas from the differentglands. Although complete saliva is a mixture of secretions the designof a saliva substitute has to be a homogenous system.

The criterion for a Theologically adequate saliva imitation canpreferably be set at a viscosity η' between 1.5 and 3 mPa·s and anelasticity between 0.1 and 1 mPa·s at Y 1.5 s⁻¹. This range reflects thevisco-elasticity of complete human saliva and saliva from the differentglands (see FIG. 1) (Van der Reijden et al., 1993).

EXAMPLE 2

1. Materials and methods

Polyacrylic acid (PAA) which is available in the pharmaceuticalqualities as Carbopol 974P® and Carbopol 934P®, has the particularproperty that it has a synergistic effect in respect of inter alia thehigh-molecular saliva mucin MG1. This has been determined in asubsequent experiment. Isolated human high-molecular saliva mucin fromtotal saliva was incubated with PAA in a viscosity comparable to that ofsaliva. After overnight incubation the visco-elasticity was measured.

2. Results and discussion

It was found herefrom that the viscosity of a mixture of PAA and MG1resulted in a higher viscosity than might be anticipated on the groundsof their individual viscosities (FIG. 9). Mixtures of PAA with water andMG1 with water served as controls. At a ratio of 1:1 this gave anincrease in-the viscosity of ±300% and an increase in the elasticity of±250%, see FIG. 9. This can mean the following in vitro. Xerostomiapatients who can produce a residual volume of saliva sometimes also havea quantity of mucin in their saliva. Because it is known that salivamucins can adhere to both the surface of the teeth and to the oralmucosa, PAA could form a protective layer by adhering to this salivamucin. This provides the additional possibility of lengthening the timeof retention in the mouth so that the application frequency can belowered.

From the experiments it was found that particularly xanthane gum, Guargum, carboxymethyl cellulose, alginic acid and polyacrylic acid wereexceptionally suitable polymers for application in a therapeuticcomposition according to the invention. Dissolved in HPLC-water theygave a clear visco-elastic solution. It was found from the experimentsthat scleroglucan in particular is completely ionicstrength-insensitive, pH-insensitive and Theologically suitable, andtherefore very useful for new artificial salivas. When xanthane gum isdissolved in a pH buffer at a low ionic strength (>10 mM NaCl), thispolymer is likewise suitable.

The invention provides new compositions which can be used for variousapplications, such as in saliva substitutes or additives, tear watersubstitutes or additives, mouth rinses, toothpastes etc.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the average viscosity and elasticity as a function of theoscillating shear rate of clarified ron-stimulated complete saliva o:seven healthy people (taken three times). T=13.0° C.±1.5° C.

--Δ-- represents the viscosity, and

--∘-- represents the elasticity. Error lines represent the standarddeviation.

FIG. 2 shows the viscosity of xanthane gum, two types of guar gum andCMC measured as a function of the shear rate. The concentration of thepolysaccharides was chosen within the range of the CCHS viscosity.

represents 0.01% xanthane gum;

represents 0.01% scleroglucan;

represents 0.1% guar gum S;

represents 0.1% guar gum P; and

represents 0.03% CMC.

FIG. 3 shows the elasticity of xanthane gum, two types of guar gum andCMC at a concentration in which the viscosity corresponds with the CCHSviscosity.

represents 0.01% xanthane gum;

represents 0.01% scleroglucan;

represents 0.1% guar gum S;

represents 0.1% guar gum P; and

represents 0.03% CMC.

FIGS. 4 & 5 show respectively the pH-dependency of the viscosity andelasticity of polysaccharides, wherein the pH is varied from pH 3 to 9.

represents 0.05% xanthane gum;

represents 0.1% scleroglucan;

represents 0.25% guar gum P;

represents 0.1% CMC;

represents 0.2% HEC; and

represents 0.25% alginic acid.

FIGS. 6 & 7 show the ionic strength dependency of respectively theviscosity and elasticity of polysaccharides wherein theNaCl-concentration is varied from 0 to 0.5M NaCl.

represents 0.05% xanthane gum;

represents 0.1% scleroglucan;

represents 0.25% guar gum P;

represents 0.1% CMC;

represents 0.2% HEC; and

represents 0.25% alginic acid.

FIG. 8 illustrates that the increase in visco-elasticity of scleroglucanwas only observed at a 10×-concentration but not at a viscosity level ofsaliva.  represents the viscosity; and the elasticity.

Finally, FIG. 9 shows the rheological synergism of polyacrylic acid withMG1-specific viscosity and elasticity. The left-hand side of the graphshows the viscosity, the right-hand side the elasticity. represents thecombination of PAA+MG1; the calculated combination of PAA+MG1; thecombination of water+MG1;  the combination of PAA+water.

We claim:
 1. A method of using an aqueous polymer compocition to enhancethe saliva of a patient, comprising administering to a patient one ormore effective doses of a composition consisting essentially of at leastone polymer selected from the group consisting of scleroglucan andxanthane gum, wherein said polymer is present in the amount of about0.01% in combination with at least one preservative and at least oneelectrolyte.
 2. A method of using an aqueous polymer composition toenhance the saliva of a patient, comprising administering to a patientone or more effective doses of a composition consisting essentially of a1:1 admixture or polyacrylic acid and mucin, in combination with atleast one preservative and at least one electrolyte.